Question

On a roofing job, 21 of 401 shingles had to be rejected for minor defects. what percent is this?

Answer 1

If we take 401 to be the 100%, what is 21 off of it in percentage?

$\bf \begin{array}{ccll} amount&\%\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ 401&100\\ 21&p \end{array}\implies \cfrac{401}{21}=\cfrac{100}{p}\implies p=\cfrac{21\cdot 100}{401}$